The transesterification reaction between ethylene glycol and dimethyl terephthalate and polycondensation of the product in the presence of lead fluoride is taught in U.S. Pat. No. 3,457,239.
Yttrium compounds, including yttrium fluoride, have been disclosed in U.S. Pat. No. 3,523,104 as catalysts for the polyesterification of the reaction product of a dicarboxylic acid or ester-forming derivative thereof with a glycol.
A combination of manganese and lithium compounds have been used as ester-interchange reaction catalysts to prevent scale formation in the production of polyesters from a dialkyl ester of terephthalic acid and a glycol according to U.S. Pat. No. 4,057,534.
Finally, the fluoride-promoted esterification of carboxylic acids, usually by their reaction with alkyl halides, is discussed in a review article by J. N. Clark-Chemical Review, 1980, 80, 429-452.